The present invention generally relates to facsimile machines, and more particularly to a facsimile machine having an error correction mode (ECM) in conformance with the CCITT recommendations.
The ECM is a mode in which an image information is transmitted in blocks which are constituted by a plurality of data frames in conformance with a high level data link control (HDLC) procedure, and when a receiving side facsimile machine (hereinafter simply referred to as a destination) detects a transmission error a transmitting side facsimile machine (hereinafter simply referred to as a source) retransmits a data frame in which the error is detected. An error correction code is transmitted with the image information in frames, and the transmission error is detected be using the error correction code.
For this reason, in order to enable retransmission of the requested data frame from the source, it is necessary for the source to temporarily store one block of image information which is transmitted. In addition, when one received block of image information contains an error, the destination must receive the retransmitted frame data which corresponds to the frame data in which the error was detected. Hence, the destination must also temporarily store the received image information so that one block of image data may be constituted using the retransmitted frame data which contains no error.
Accordingly, the facsimile machine having the ECM is provided with an ECM buffer memory for temporarily storing one block of image information. For example, the ECM buffer memory has a memory capacity of 64 kbits which is normally sufficient to store an image information amounting to one page of document.
When the facsimile machine having the ECM is receiving a transmission, a plotter may break down, a paper jam may occur in the plotter and the plotter may run out of recording paper during a recording of an image. When this non-recordable state of the plotter occurs in a facsimile machine which is not provided with a so-called store and forward (SAF) image memory, the reception process of the destination is discontinued by transmitting to the source a disconnect (DCN) signal or a procedural interrupt negative (PIN) signal each of which is a line disconnect instruction. On the other hand, in the case of the facsimile machine provided with the so-called SAF image memory, the received image information is stored in the SAF image memory but the DCN signal or the like is transmitted to discontinue the reception process when the memory capacity of the SAF image memory becomes insufficient to store all the image information.
In the above described case, one block of the received image information is temporarily stored in the ECM buffer memory. However, when the reception process is discontinued, the content of the ECM buffer memory is erased at the same time. For this reason, there is a problem in that the received image information amounting to one page of document is erased without ever being recorded on the plotter.
Generally, the image memory for storing the image information is of a type which erases (or clears) the content thereof when the supply of power is cut off. Thus, when the image information which is not yet recorded is stored in the ECM buffer memory but the power supply to the facsimile machine is cut off due to a power failure or the like, the image information stored in the ECM buffer memory is erased.
Conventionally, when the power supply is cut off, the facsimile machine records and outputs after the supply of power is resumed a report indicating that the power supply was cut off, so that the operator is informed of the erasure of the received image information stored in the SAF image memory. But conventionally, there is a problem in that the operator is not informed of the erasure of the image information stored in the ECM buffer memory due to the cutoff of the power supply, and the operator has no means of knowing this erasure of the image information stored in the ECM buffer memory.